Similar processes and devices are known from European Paten Disclosure Document #EP-OS 0,260,331. In the prior-art process, the workpiece layers are fed to each other by conveying means. The conveying means comprise rail-guided carriages on which clamps are arranged holding the upper end of the workpiece layers. These conveying means have track sections directed in parallel to one another in a scanning station and an aligning station. To make possible the mutual alignment of the workpiece layers, the clamps are arranged on the carriages of one of the conveying means by means of a holding head which is movable in a plurality of directions in relation to the carriage carrying it. This holding head carries a magnetizable plate which comes into frictionally engaged contact in the aligning station with a permanent magnet that is fastened to the adjacent carriage of the other conveying means. Using an adjusting device of the stationary aligning station, the movable holding head of the clamps on the first-named carriage is adjusted, corresponding to the scanning result, such that the two workpiece layers that are adjacent to one another in the aligning station will reach the predetermined relative position. Based on the frictional engagement between the magnetizable plate on the holding head of one carriage and the permanent magnet on the other carriage, this relative position is maintained when the two carriages move together from the aligning station into the subsequent processing station after alignment of the workpiece layers.
This design is relatively complicated, because it requires an adjustable holding head that is adjustable in a plurality of directions at each of the carriages of one conveying means. In addition, to adjusting the holding heads, the adjusting device must exert a considerable force to reach the specified relative position of the two workpiece layers in order to overcome the frictional force between the magnetizable plate and the permanent magnet, which must, as is explained, be strong enough to maintain the relative position, once set, between the permanent magnet and the plate and consequently the aligned position of the workpiece layers.